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Shingles and chickenpox (Varicella-zoster virus)

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of shingles and chicken pox.

Alternative Names

Chicken pox; Herpes zoster; Postherpatic neuralgia

Introduction

Shingles and chickenpox were once considered separate disorders. Researchers now know that they are both caused by a single virus of the herpes family known as varicella-zoster virus (VZV). The word herpes is derived from the Greek word "herpein," which means "to creep," a reference to a characteristic pattern of skin eruptions. VZV is still referred to by separate terms:

Varicella: The primary infection that causes chickenpox
Herpes zoster: The reactivation of the virus that causes shingles

Varicella (Chickenpox). When patients with chickenpox cough or sneeze, they expel tiny droplets that carry the virus. If a person who has never had chickenpox or been vaccinated inhales these particles, the virus enters the lungs. From here it passes into the bloodstream. When it is carried to the skin it produces the typical rash of chickenpox.

Chickenpox is caused by the varicella-zoster virus, a member of the herpes virus family. The same virus also causes herpes zoster, shingles, in adults. Chickenpox is extremely contagious, and can be spread by direct contact, droplet transmission, and airborne transmission. Symptoms range from fever, headache, stomach ache, or loss of appetite before breaking out in the classic pox rash. The rash can consist of several hundred small, itchy, fluid-filled blisters over red spots on the skin. The blisters often appear first on the face, trunk, or scalp and then spread to other parts of the body

Herpes Zoster (Shingles). The varicella virus also travels to nerve cells called dorsal root ganglia. These are bundles of nerves that transmit sensory information from the skin to the brain. Here, the virus can hide from the immune system for years, often for a lifetime. This inactivity is called latency.

Click the icon to see an image of shingles.

If the virus becomes active after being latent, it causes the disorder known as shingles. The virus in this later form is referred to as herpes zoster . The virus spreads in the ganglion and to the nerves connecting to it. Nerves most often affected are those in the face or the trunk. The virus can also spread to the spinal cord and into the bloodstream. In 2006, scientists at the U.S. Institutes of National Health identified a specific protein, called insulin-degrading enzyme, which causes the varicella-zoster virus to spread throughout cells in the body. The scientists hope that this discovery may eventually help in developing new drug therapies for treating shingles.

It is not clear why the varicella virus reactivates in some people but not in others. In many cases, the immune system has become impaired or suppressed from certain conditions such as AIDS, other immunodeficient diseases, or certain cancers or drugs that suppress the immune system. Aging itself increases the risk for shingles.

Other Herpes Viruses

The varicella-zoster virus belongs to a group of herpes viruses that includes eight human viruses (it also includes animal viruses as well). Herpes viruses are similar in shape and size and reproduce within the structure of a cell. The particular cell depends upon the specific virus. The human herpes viruses are:

Herpes Simplex Virus 1 (HSV-1; causes cold sores and sometimes genital herpes)
Herpes Simplex Virus 2 (HSV-2; causes genital herpes and sometimes cold sores)
Varicella-zoster Virus (VZV; causes chickenpox and shingles)
Cytomegalovirus (CMV; causes mononucleosis and retinitis)
Epstein-Barre Virus (EBV; causes mononucleosis
Human Herpesvirus 6 (HHV6; causes roseola)
Human Herpesvirus 7 (HHV7; causes roseola)
Human Herpesvirus 7 (HHV8; causes Kaposi's sarcoma)

All herpes viruses share some common properties, including a pattern of active symptoms followed by latent inactive periods that can last for months, years, or even for a lifetime. [For more information, see In-Depth Report #52: Herpes simplex.]

Review Date: 3/15/2007
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

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